Edward L. Thorndike

From New World Encyclopedia

Edward Lee Thorndike (August 31, 1874 – August 9, 1949) was an American educational and comparative psychologist who spent nearly his entire career at Teachers College, Columbia University. He formulated the basic law of operant learning, the law of effect. Thorndike’s importance for the twentieth century psychology is in his methodological and theoretical approach to animal learning and his formulation of a stimulus-response (S-R) psychology that he called "connectionism." Thorndike was striving to understand the learning process, through studying animals, to develop applications in education and thus benefit society. Although not formally a behaviorist, Thorndike's work was foundational to the development of American behavioristic psychology.


Edward Lee Thorndike was born on August 31, 1874, in Williamsburg, Massachusetts, into a Methodist minister family. Edward was raised in an environment marked by sternness and religious exhortation, but as a young adult chose to eschew religion and pursue a personal code derived from his commitment to inductivism.

Edward Thorndike was attracted to psychology, when he read William James’ “Principles” for a debate competition at his undergraduate school, Wesleyan University, in Connecticut. Thorndike completed his Bachelors degree at Wesleyan, in 1895, and went on with his graduate work at Harvard University, where he eagerly signed up for courses with William James and eventually majored in psychology.

His first research interest was children and pedagogy but, no child subjects being available, Thorndike took up the study of learning in animals. William James gave him a place to work in his basement after Thorndike failed to secure official research space from Harvard. Thorndike completed his Masters in 1897. James McKeen Cattell offered Thorndike a fellowship at Columbia University, where he defended his doctoral dissertation, “Animal Intelligence: An Experimental Study of the Associative Processes in Animals,” in 1898. He expanded and published his dissertation in 1911.

In 1899, Columbia University took over the New York College for the Training of Teachers, and Thorndike joined the faculty of the consolidated Columbia Teachers College. He remained there for the rest of his career, pursuing educational issues, especially in intelligence testing.


In the early 1900s, Edward Thorndike published two works outlining applications of learning and testing principles—Educational Psychology (1903) and Introduction to Theory of Mental and Social Measurement (1904). Both texts became necessary reading for a generation of students of psychology and the social sciences. Thorndike described intelligence through a somewhat elementaristic approach by stressing that intelligence is composed of a number of abilities. Although Thorndike’s views on association processes earned him greater fame in behavioristic psychology, his capacity to use his research reflected an applied direction, entirely consistent with American functionalism.

Thorndike’s work on animal behavior and the learning process led to the theory of "connectionism." Thorndike wrote, “Our reasons for believing in the existence of other people’s minds are our experience of their physical actions.” He formulated the doctrine that consciousness is unnecessary for learning. Unlike Ivan Pavlov, Thorndike practiced a purely behavioral psychology without reference to physiology.

On the other hand, Thorndike proposed a principle of “belongingness” that violates a basic principle of classical conditioning, namely, that those elements most associated in space and time will be connected in learning. The sentences “John is a butcher, Harry is a carpenter, Jim is a doctor,” presented in the list like this, would make butcher-Harry a stronger bond than butcher-John, if the classical conditioning contiguity theory were correct. However, this is clearly not the case. John and butcher “belong” together (because of the structure of the sentences) and so will be associated, and recalled together. This principle of belongingness resembled Gestalt psychology rather than behaviorism.

Thorndike examined problem solving strategies in a variety of species, which he tested in "puzzle boxes" consisting of a series of chambers designed to reward specific responses. Thorndike was impressed with his subjects’ gradual acquisition of successful responses by trial-and-error learning and by accidental success. These observations led him to conclude that there were two basic principles of learning: exercise and effect.

Thorndike’s Experiments

Thorndike’s experiments on problem solving behavior resulted in significant findings that were highly regarded at the time of Ivan Pavlov and John B. Watson and are still recognized. Thorndike never intended to be a system builder, as Watson did, and his earlier, more theoretical work was later replaced by a shift to more practical problems of human learning and education.

Among Thorndike's most famous contributions were his research on how cats and other animals learned to escape from puzzle boxes and his related formulation of the law of effect. Thorndike placed an animal in one of many puzzle boxes, each of which could be opened by the animal in a different way. When the animal escaped it was fed. Thorndike’s setup is an example of what would later be called "instrumental conditioning" or "instrumental learning": An animal makes some response, and if it is rewarded—in Thorndike’s case with escape and food—the response is learned. If the response is not rewarded, it gradually disappears.

The law of effect states that responses that are closely followed by satisfying consequences become associated with the situation, and are more likely to reoccur when the situation is subsequently encountered. Conversely, if the responses are followed by aversive consequences, associations to the situation become weaker. The puzzle box experiments were motivated in part by Thorndike's dislike for statements that animals made use of extraordinary faculties such as insight in their problem solving: "In the first place, most of the books do not give us a psychology, but rather a eulogy of animals. They have all been about animal intelligence, never about animal stupidity." (Animal Intelligence, 1911)

Thorndike meant to distinguish clearly whether or not cats escaping from puzzle boxes were using insight. Thorndike's instruments in answering this question were "learning curves" revealed by plotting the time it took for an animal to escape the box each time it was in the box. He reasoned that if the animals were showing "insight," then their time to escape would suddenly drop to a negligible period, which would also be shown in the learning curve as an abrupt drop; while animals using a more ordinary method of trial and error would show gradual curves. His finding was that cats consistently showed gradual learning.

Thorndike interpreted the findings in terms of associations. He asserted that the connection between the box and the motions the cat used to escape was "strengthened" by each escape. A similar, though radically reworked idea was taken up by B. F. Skinner in his formulation of operant conditioning. The associative analysis went on to figure largely in behavioral work through mid-century, and became evident in some later work in behavior as well as modern connectionism.

Law of Effect

The law of effect was described by Thorndike in 1898. It holds that responses to stimuli that produce a satisfying or pleasant state of affairs in a particular situation are more likely to occur again in the situation. Conversely, responses that produce a discomforting, annoying, or unpleasant effect are less likely to occur again in the situation.

Thorndike’s second law is the law of exercise: “Any response to situation will, all other things begin equal, be more strongly connected to the number of times it has been connected with that situation, and to the average vigor and duration of the connections.”

Thorndike contended that these two laws can account for all behavior, no matter how complex: It is possible to reduce “the processes of abstraction, association by similarity and selective thinking to mere secondary consequences of the laws of exercise and effect.” Thorndike analyzed language as a set of vocal responses learned because parents reward some of a child’s sounds but not others. The rewarded ones are acquired and the non-rewarded ones are unlearned, followed the law of effect.

These laws are important in understanding learning, especially in relationship to operant conditioning. However their status is controversial: particularly in relation to animal learning, it is not obvious how to define a "satisfying state of affairs" or an "annoying state of affairs" independent of their ability to induce instrumental learning, and the law of effect has therefore been widely criticized as logically circular. In the study of operant conditioning, most psychologists have therefore adopted B. F. Skinner's proposal to define a reinforcer as any stimulus which, when presented after a response, leads to an increase in the future rate of that response. On that basis, the law of effect follows tautologically from the definition of a reinforcer.

The law of effect or influences of reinforcement require active recognition by the subject. Since the effects presumably feed back to strengthen an associative bond between a response and a stimulus, some mechanism or principle of realization is needed for the subject to recognize whether the reinforcement was satisfying or not. This problem, which still plagues reinforcement theory, revolves around the need for the mediation of response-produced effects. Is some postulation of consciousness needed to adequately deal with the judgmental realization in order to act on reinforcement effects? Thorndike suggested that perhaps centers of satisfiers and annoyers may exist at a physiological level. While this explanation is not supported, Thorndike’s principles of repetition and reinforcement, in accounting for learning, are accepted.

In an influential paper of 1970, Herrnstein proposed a quantitative relationship between response rate (B) and reinforcement rate (Rf):

B = k Rf / (Rf0 + Rf)

where k and Rf0 are constants. Herrnstein proposed that this formula, which he derived from the matching law he had observed in studies of concurrent schedules of reinforcement, should be regarded as a quantification of Thorndike's law of effect. While the qualitative law of effect may be a tautology, this quantitative version is not.


The major criticism of Thorndike’s behaviorist theories may be summarized in two points. First, Thorndike’s approach restricted psychology by limiting behavior solely to the peripheral events of stimulus and response elements. In dismissing mental events, Thorndike also ignored the central mediation of stimulus and response bonds.

The second problem with Thorndike’s behaviorist theories concerns the issue of reductionism. In fact, for Thorndike, mind was reduced to behavior, and behavior, in turn, was reduced to environmental stimuli and observable responses.


Edward L. Thorndike's personal inductivism suffused connectionism, his main contribution to psychology. He developed his main ideas in his three-volume magnum opus Educational Psychology (1913-1914) as the "Laws of Learning" and remained substantially unchanged throughout his career.

Historically, Thorndike is hard to place. He did not found behaviorism, although he practiced it in his animal research. As a practicing behaviorist, but not a wholehearted one, Thorndike is considered as the major American researcher relevant to the background leading to Watsonian behaviorism. Thus, it can be understood that behaviorist psychology received its modern expression in the associationism and connectionism of Edward Thorndike, through his careful empirical documentation of the association and learning processes in animal behavior.


  • Thorndike, E. L. 1898. "Review of Evans’ Evolution, ethics and animal psychology." Psychological Review 5: 229-230.
  • Thorndike, E. L. 1899. "The mental life of the monkey." Psychological Review, Monograph Supplement, 3, No. 15.
  • Thorndike, E. L. 1911. Animal Intelligence, 2nd ed. New York, NY: Hafner. Transaction Publishers, 2000. ISBN 0765804824
  • Thorndike, E. L. 1929. Human Learning. New York, NY: Johnson Reprint Corporation. The MIT Press; New Impression edition. 1966. ISBN 0262700018
  • Thorndike, E. L. 1936. A History of Psychology in Autobiography (Vol. 3). Worcester, MA: Clark University Press.
  • Thorndike, E. L., and C. J., Herrick. 1915. "Watson’s behavior." Journal of Animal Behavior, 5, 462-470.

ISBN links support NWE through referral fees

  • Ben-David, J. and R. Collins. 1966. Social factors in the origin of a new science: The case of psychology. American Psychological Review, 31, 451-465.
  • Blumenthal, A.L. 1981. Language and Psychology: Historical Aspects of Psycholinguistics. Krieger Pub Co. ISBN 089874167X
  • Boring, E.G. 1950. A history of experimental psychology, 2nd ed. Englewood Cliffs, NJ: Prentice Hall. ISBN 0133900398
  • Brennan, J.F. 1986. History and systems of psychology. Englewood Cliffs, NJ: Prentice-Hall, Inc. ISBN 0133922189
  • Herrnstein, R. J. 1970. "On the law of effect." Journal of the Experimental Analysis of Behavior, 13, 243-266.
  • Joncich, G. 1984. The sane positivist: A Biography of E. L. Thorndike. Middletowm, CT: Wesleyan University Press. ISBN 0819560928
  • Leahey, Th. H. 1991. A History of Modern Psychology. Englewood Cliff, NJ: Prentice Hall. 3rd edition. 2000. ISBN 0130175730
  • Skinner, B. F. 1950. "Are theories of learning necessary?" Psychological Review, 57, 193-216.
  • Spence, K. 1948. "Postulates and methods of behaviorism." Psychological Review, 55, 67-78.
  • Stevens S. S. 1935. "The operational definition of psychological concepts." Psychological Review, 42, 517-527.
  • Williams, K. 1931. "Five behaviorisms." American Journal of Psychology. 22, 337-361.
  • Woodworth, R. S. 1924. "Four varieties of behaviorism." Psychological Review, 31, 257-264.


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